Various high molecular weight light emitting materials (polymeric fluorescent substances) have been studied, because they are soluble in a solvent and thus able to form a light emitting layer by an application method unlike lower molecular weight ones. For example, the followings are disclosed: poly(p-phenylene vinylene) (sometimes referred to as “PPV” hereinafter) (WO9013148, JP-A-3-244630, Appl. Phys. Lett., vol. 58, page 1982 (1991) or the like), polyfluorene (Jpn. J. Appl. Phys. vol. 30, page L1941 (1991), a polypara-phenylene derivative (Adv. Mater., vol. 4, page 36 (1992)), and the like.
In order to utilize a feature of a polymeric fluorescent substance, that is, the feature with which they are soluble in a solvent and thus able to form a light emitting layer by an application method, a polymeric fluorescent substance further excellent in solubility has been required.